1. Field of the Invention
This invention relates to a safe and explosion preventing sealed type battery.
2. Description of the Prior Art
Generally, in sealed type batteries such as alkaline storage batteries, when the battery is overcharged or overdischarged, an excess gases exceeding the capacity of the electrode body for absorbing the gas will be generated from time to time. When this pressure within the battery becomes higher than the limited resisting pressure of the battery sealed part, an explosion accident will often occur and will damage the instrument being used. Therefore, various contrivances have been suggested whereby, when the internal pressure of the battery becomes higher than the limited resisting pressure, this internal pressure will be alllowed to escape to prevent the explosion of the battery. For example, as represented by U.S. Pat. No. 3,262,819, there is a method wherein a film is provided within a battery so that, when the internal pressure rises abnormally, the film will expand and is broken by a thrusting blade located outside the film and the internal gas may escape through there. In this method, a comparatively large space is required to within the battery and the component parts are many. It is also suggested to form a cruciform stamp on a battery can so that, when the internal pressure rises abnormally, the can may tear open. However, in fact, there have been many difficulties with such prior art devices.